The present invention pertains to polynucleotides derived from staphylococcal genes encoding resistance to streptogramin A or to streptogramin B and chemically related compounds. This invention also relates to the use of the polynucleotides as oligonucleotide primers or probes for detecting Staphylococcal strains that are resistant to streptogramin A or to streptogramin B and related compounds in a biological sample.
In another embodiment, the present invention is directed to the full length coding sequences of the staphylococcal genes encoding for resistance to streptogramin A or to streptogramin B from Staphylococcus and to the polypeptides expressed by these full length coding sequences.
Further, this invention relates to the use of the expressed polypeptides to produce specific monoclonal or polyclonal antibodies that serve as detection means in order to characterize any staphylococcal strain carrying genes encoding resistance to streptogramin A or to streptogramin B.
The present invention is also directed to diagnostic methods for detecting specific strains of Staphylococcus expected to be contained in a biological sample. The diagnostic methods use the oligonucleotide probes and primers as well as the antibodies of the invention.
Streptogramins and related compounds (antibiotics) produced by streptomycetes can be classified as A and B compounds according to their basic primary structures (Cocito, 1979). Compounds of the A group, including streptogramin A (SgA), pristinamycin IIA (PIIA), virginiamycin M, mikamycin A, or synergistin A, are polyunsaturated cyclic macrolactones. Compounds of the B group, including streptogramin B (SgB), pristinamycin B (PIB), virginiamycin S, mikamycin B, and synergistin B, are cyclic peptidic macrolactones (Cocito, 1979). Compounds of both groups, A and B, bind different targets in the peptidyltransferase domain of the 50S ribosomal subunit and inhibit protein elongation at different steps (Aumercier et al., 1992; Di Giambattista et al., 1989).
A decrease in the dissociation constant of PIB is observed in the presence of PIIA because this latter antibiotic provokes a conformational modification of the bacterial ribosome at the binding sites of these molecules. Thus, A and B compounds, which are bacteriostatic when used separately, act synergistically when combined and become bactericidal, mainly against Gram-positive bacteria.
Natural mixtures such as pristinamycin (Pt), synergistin, virginiamycin and mikamycin, are used orally and topically. A semi-synthetic injectable streptogramin, RP59500, consisting of a mixture of derivatives of A and B compounds (Dalfopristin and Quinupristin, respectively) is currently undergoing in vivo experimental and clinical trials (J. Antimicrob. Agents Chemother. 30 (Suppl. A), entire volume, 1992; Entenza et al., 1995; Fantin et al., 1995; Griswold et al., 1996; Torralba et al., 1995). Staphylococcal resistance to synergistic mixtures of A and B compounds (Pt MICxe2x89xa72 xcexcg/ml) is always associated with resistance to A compounds (PIIA MICxe2x89xa78 xcexcg/ml), but not necessarily with resistance to B compounds (Allignet et al., 1996).
To date, four genes encoding resistance to A compounds have been isolated from staphylococcal and enterococcal plasmids. The genes vat (Allignet et al., 1993), vatB (Allignet and El Solh, 1995), and satA (Rende-Fournier et 1993) encode related acetyltransferases (50.4-58.3% amino acids), which inactivate streptogramin A and similar compounds. The staphylococcal gene vga (Allignet et al., 1992) encodes an ATP-binding protein probably involved in the active efflux of A compounds. Nevertheless, there continues to exist a need in the art for polynucleotides specific for Staphylococcus resistant to streptogramin A and/or B and related compounds.
Accordingly, this invention aids in fulfilling this need in the art. In particular, this invention provides a purified peptide comprising an amino acid sequence selected from the group consisting of:
a) SEQ ID NO: 4 which corresponds to the complete amino acid sequence of Vga B or fragments derived from SEQ ID NO: 4 containing at least 10 amino acids;
b) SEQ ID NO: 5 which corresponds to the complete amino acid sequence of Vat C or fragments derived from SEQ ID NO: 5 containing at least 10 amino acids;
c) SEQ ID NO: 6 which corresponds to the complete amino acid sequence of Vgb B or fragments derived from SEQ ID NO: 6 containing at least 10 amino acids;
d) SEQ ID NO: 7 which corresponds to a fragment of the amino acid sequence of Vgb B;
e) SEQ ID NO: 8 which corresponds to a fragment of the amino acid sequence of Vga B;
f) SEQ ID NO: 9 which corresponds to a fragment of the amino acid sequence of Vat C; and
g) SEQ ID NO: 10 which corresponds to a fragment of the amino acid sequence of Vat C.
This invention additionally provides a purified polynucleotide comprising the nucleotide sequence selected from the group consisting of:
a) SEQ ID NO: 1 which corresponds to the complete nucleic acid sequence of vga B or fragments derived from SEQ ID NO: 1 containing 15 to 40 nucleotides;
b) SEQ ID NO: 2 which corresponds to the complete nucleic acid sequence at vat C or fragments derived from SEQ ID NO: 2 containing 15 to 40 nucleotides;
c) SEQ ID NO: 3 which corresponds to the complete nucleic acid sequence of vgb B or fragments derived from SEQ ID NO: 3 containing 15 to 40 nucleotides;
d) SEQ ID NO: 11 which corresponds to the nucleic acid sequence encoding the polypeptide of SEQ ID NO: 7;
e) SEQ ID NO: 12 which corresponds to the nucleic acid sequence encoding the polypeptide of SEQ ID NO: 8;
f) SEQ ID NO: 13 which corresponds to the nucleic acid sequence encoding the polypeptide of SEQ ID NO: 9; and
g) SEQ ID NO: 14 which corresponds to the nucleic acid sequence encoding the polypeptide of SEQ ID NO: 10.
Furthermore, this invention includes a purified peptide comprising the amino acid sequence encoded by the nucleotide sequence selected from the group consisting of:
a) SEQ ID NO: 1,
b) SEQ ID NO: 2,
c) SEQ ID NO: 3,
d) SEQ ID NO: 11,
e) SEQ ID NO: 12,
f) SEQ ID NO: 13, and
g) SEQ ID NO: 14.
This invention also provides a composition comprising purified polynucleotide sequences including at least one nucleotide sequence of the genes selected from the group consisting of polypeptides or genes or cDNA of vgaB, vatC, and vgbB, which are useful for the detection of resistance to streptogramin A or to streptogramin B and related compounds.
In another embodiment, this invention provides a composition of polynucleotide sequences encoding resistance to streptogramins and related compounds, or inducing this resistance in Gram-positive bacteria, wherein the composition comprises a combination of at least two of the following nucleotide sequences: a) a nucleotide sequence encoding an acetyltransferase conferring resistance to streptogramin A and related compounds, b) a nucleotide sequence encoding a molecule containing ATP binding motifs conferring resistance to streptogramin A and related compounds; and c) a nucleotide sequence encoding a lactonase conferring resistance to streptogramin B and related compounds.
Furthermore, this invention provides a composition of polynucleotide sequences, wherein the sequence encoding a molecule containing ATP binding motifs confers resistance to Staphylococci and particularly to S. aureus, and wherein the polynucleotide sequence corresponds to a vgaB nucleotide sequence represented by SEQ ID NO: 1 or a sequence having at least 70% homology with vgaB complete nucleotide sequence, or to a polynucleotide hybridizing with SEQ ID NO: 1 under stringent conditions, or to a fragment containing between 20 and 30 nucleotides of SEQ ID NO: 11 or SEQ ID NO: 12, or wherein the polynucleotide sequence encodes a polypeptide having at least 60% homology with the complete SEQ ID NO: 4 or with SEQ ID NO: 7 or SEQ ID NO: 8.
Furthermore this invention relates to a composition of polynucleotide sequences, wherein the sequence encoding an acetyltransferase confers resistance to streptogramin A and related compounds in Staphylococci, and particularly in S. cohnii, and wherein the polynucleotide sequence corresponds to a vatC nucleotide sequence represented by SEQ ID NO: 2 or a sequence having at least 70% homology with vatC complete nucleotide sequence, or to a polynucleotide hybridizing with SEQ ID NO: 2 under stringent conditions, or to a fragment containing between 20 and 30 nucleotides of SEQ ID NO: 13 or SEQ ID NO: 14, or wherein the polynucleotide sequence encodes a polypeptide having at least 60% homology with the complete SEQ ID NO: 5 or with SEQ ID NO: 9 or SEQ ID NO: 10.
This invention also provides a composition of polynucleotide sequences, wherein the sequence encoding a lactonase confers resistance to streptogramin B and related compounds in Staphylococci and particularly in S. cohnii, and wherein the polynucleotide sequence corresponds to a vgbB nucleotide sequence represented in SEQ ID NO: 3 or a sequence having at least 70% homology with vgbB complete nucleotide sequence, or to a polynucleotide hybridizing with SEQ ID NO: 3 under stringent conditions, or to a fragment containing between 20 and 40 nucleotides of SEQ ID NO: 3, or wherein the polynucleotide sequence encodes a polypeptide having at least 60% homology with the complete SEQ ID NO: 6.
The invention also contemplates a composition of polynucleotide sequences, wherein at least a vatB nucleotide sequence encoding an acetyltransferase conferring resistance to streptogramin A and related compounds is included in addition to a vgaB nucleotide sequence encoding a molecule containing ATP binding motifs conferring resistance to streptogramin A.
Additionally, the invention includes a purified polynucleotide that hybridizes specifically under stringent conditions with a polynucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, and SEQ ID NO: 14.
The invention further includes polynucleotide fragments comprising at least 10 nucleotides capable of hybridization under stringent conditions with any one of the nucleotide sequences enumerated above.
In another embodiment of the invention, a recombinant DNA sequence comprising at least one nucleotide sequence enumerated above and under the control of regulatory elements that regulate the expression of resistance to antibiotics of the streptogramin family in a defined host is provided.
Furthermore, the invention includes a recombinant vector comprising the recombinant DNA sequence noted above, wherein the vector comprises the plasmid pIP1633 or plasmid pIP1714.
The invention also includes a recombinant cell host comprising a polynucleotide sequence enumerated above or the recombinant vector defined above.
In still a further embodiment of the invention, a method of detecting bacterial strains that contain the polynucleotide sequences set forth above is provided.
Additionally, the invention includes kits for the detection of the presence of bacterial strains that contain the polynucleotide sequences set forth above.
The invention also contemplates antibodies recognizing peptide fragments or polypeptides encoded by the polynucleotide sequences enumerated above.
Still further, the invention provides for a screening method for active antibiotics and/or molecules for the treatment of infections due to Gram-positive bacteria, particularly staphylococci, based on the detection of activity of these antibiotics and/or molecules on bacteria having the resistance phenotype to streptogramins.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.